Jabir bin'Abdullah (RA) reported that when Asma' bint Umais gave birth (to a child) in Dhu'I-Hulaifa. Allah's Messenger (ﷺ) commanded Abu Bakr (RA) (to convey to her) that she should take a bath and enter into the state of Ihram.
Hadith ReferenceSahih Muslim / The Book of Pilgrimage / Hadith: 1210